I did look (I'm slowly replacing every radiator in the house as I renovate) plumber gave me a few horror stories though so I've used radiator outlet and been very impressed. I'm sure some are good but wasn't worth the risk to me. Would recommend radiator outlet was Quick delivery, cheaper than many (but not the cheapest), good quality.
You've got to be really careful with radiators - the cheap no-name ones imported from China en-masse are usually made from thin low quality steel & have a poor application of paint, & will be showing rust marks around the joints/fittings after a few years.
Same issue with the cheap ones from Screwfix - I had a towel radiator in the last house that was rusting through after 4 years.
Personally I'd swallow the cost & plump for decent ones from a brand who have a reputation to uphold - It's a job you just want to do once.
I was going to buy replacement modern "designer" radiators from a shop - like B and Q or Screwfix. Then looked on eBay and saw what looks like the same things for less than half the price from lots of sellers. Has anyone bought from eBay? Is the quality the same - looks too good to be true at those prices.